In particular, Iain says it's a "sop" to go on allowing Scots MPs to vote on English laws at Third Reading.Â But I think Iain may be understating the importance of part of the new Tory package: a new parliamentary undertaking that would prevent any party using Scottish votes to block amendments made by English MPs.

That new convention is far more important than it seems.Â And before you dismiss it as simply a rhetorical device, consider that a similar convention currently exists over the decisions of the Scottish Parliament. In constitutional law, there's nothing to stop the House of Commons reversing any decision made by Holyrood, since sovereign power still rests at Westminster.Â But in political reality, it would never happen.

And so, Tories hope, the new deal Ken Clarke has drawn up, would come to hold similar status, another unwritten but unbreakable rule.Â